Shows "Unable to get repr for <class 'django.db.models.query.QuerySet'>" while retrieving data

It looks like you are using Python 3.x

Change your

def __unicode__(self):

to

def __str__(self):

These problems arise when you have a problem with your DB.
Very excellent answer by @Shubho Shaha. I encounter the same problem and I debug it by following method.

class G(models.Model):
      subscription_startdate = models.DateField(default=timezone.datetime.today().date()) 
      ...
      ...

I tried to access each field separately using .values and I found a problem with my DateField column because I assign wrong default value

I faced this problem due to bad variable naming. In my case:

class SomeModel(models.Model):
    User = models.ForeignKey(User, .....)
    #  other fields ...
    #       .
    #       .
    #       .

The issue here is that I named the field user with capital ‘U’, i-e "User", which is actually the name of my django custom User Model, which, for some reason, django didn’t like that and and got angry :p.

So I simply made the user field lower case, i-e :

user = models.ForeignKey(User, .....)  # User --> user

My solution was simple.

class Report(TimestampedModel):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    report_id = models.CharField(max_length=255, blank=True, null=True)
    sector = models.CharField(max_length=255, blank=True, null=True)

def __str__(self):
        return self.project_name

What caused my issue was that I was using a field (project_name) that was not part of the model fields. So I changed it to what was in the model and I stopped getting the error. .

def __str__(self):
        return self.sector

This is how my problem got fixed.

Update
Another cause for the above issue as I found out here is that the returned data from the def str(self) method should be a string. Anything other than that will throw the above error.

A fix can be to convert the data type of what youre returning to a string like this;

def __str__(self):
        return str(self.date_answered)

This can happen when you do not specify the model name correctly in the serilizer. In my case this was the mistaken, and when i corrected it, it worked. here is an example;
model code

class ResourcesChosen(models.Model):
    resources = models.ForeignKey(Resource, null=True, default=None, on_delete=models.CASCADE)
    poll = models.ForeignKey(Polls, null=True, default=None, on_delete=models.CASCADE)
    appusers = models.ForeignKey(AppUser, null=True, default=None, on_delete=models.CASCADE)
    farmers = models.ForeignKey(Farmer, null=True, default=None, on_delete=models.CASCADE)
    longitude = models.DecimalField(max_digits=11, decimal_places=7, null=True, blank=True)
    latitude = models.DecimalField(max_digits=11, decimal_places=7, null=True, blank=True)

    def __str__(self):
        return self.resources

Serializer code

class ResourcesChosenSerializer(serializers.ModelSerializer):
    class Meta:
        model = Replies
        fields = (
            'id',
            'resources'
            'poll'
            'appusers',
            'farmers',
            'latitude',
            'longitude',
        )

As you can see, the model name is different from what i specified in the model and that was causing issues. The correct way is;

class ResourcesChosenSerializer(serializers.ModelSerializer):
    class Meta:
        model = ResourcesChosen
        fields = (
            'id',
            'resources'
            'poll'
            'appusers',
            'farmers',
            'latitude',
            'longitude',
        )

This fix eliminated the problem, "Unable to get repr for <class ‘django.db.models.query.QuerySet’>" while retrieving data